1. Field of the Invention
The present invention relates to a reciprocating-piston type refrigerant compressor adapted for use in compression of a refrigerant gas for an air-conditioning system of an automobile, which is provided with a refrigerant-gas-suction mechanism including a rotary-type suction valve fixed to a rotatable drive shaft to which an external drive force is applied by the engine of the automobile so as to operate the compressor. More particularly, it relates to a rotary-type suction valve mechanism, accommodated in the above-described reciprocating-piston type refrigerant compressor, which has an improved internal construction enabling it to maintain adequate volumetric compression efficiency and also adequate drive force-to-work efficiency while suppressing a rise in the temperature of the discharged refrigerant gas.
2. Description of the Related Art
A typical reciprocating-piston-type compressor is disclosed in, for example, Japanese Unexamined Patent publication (Kokai) No. 59-145378, in which a swash-plate-type rotation-to-reciprocation conversion mechanism is mounted on a drive shaft to reciprocate the pistons in a plurality of axial cylinder bores formed in a cylinder block arranged to be in parallel with the rotating axis of the drive shaft. The reciprocation of the pistons in the cylinder bores of the cylinder block pumps refrigerant gas into the cylinder bores, compresses the pumped refrigerant gas within the cylinder bores, and discharges the compressed refrigerant gas from the cylinder bores. The above-described reciprocating-piston type compressor is provided with housings attached to both ends of the cylinder block via valve plates, and the housings define therein suction chambers for receiving the refrigerant gas before compression to be supplied into the cylinder bores and discharge chambers for receiving the refrigerant gas after compression discharged from the cylinder bores. The supply of the refrigerant gas from the suction chambers toward the cylinder bores is carried out through suction ports bored in the valve plates when the suction ports are opened by suction valves attached to the inner face of each valve plate. The suction valve in the shape of a flapper type valve is arranged so as to be moved from a suction-port closing position toward a suction-port opening position in response to a reduction of gas pressure in the related cylinder bore during the movement of the associated reciprocating piston from the top dead center thereof toward the bottom dead center thereof in the cylinder bore. The discharge of the compressed refrigerant gas from each of the respective cylinder bores toward the discharge chambers of the housings carried out through discharge ports bored in the valve plates when the discharge ports are opened by flapper-type discharge valves attached to the outer face of each of-the valve plates. Each discharge valve is moved from a discharge-port closing position to a discharge-port opening position when the related piston is moved from the bottom dead center thereof toward the top dead center thereof within the corresponding cylinder bore.
In the above-described conventional reciprocating-piston type compressor, the flapper-type suction valves made of an elastic material are elastically urged toward the respective suction-port closing positions, and are moved toward the respective suction-port opening positions against the elastic force exerted by themselves, Namely, the suction valve is not able to be quickly moved from the suction-port closing position thereof to the suction-port opening position thereof during the suction phase of the related cylinder bore, and accordingly, a large amount of loss of suction pressure occurs, which lowers the volumetric compression efficiency.
Further, in the conventional reciprocating-piston type compressor, it is not possible to prevent a minor part of the compressed gas from remaining in the cylinder bores in the phase of an ending stage of a discharging operation. That is, the minor part of the compressed refrigerant gas remains as a high pressure residual gas in a small space between the pistons at the top dead center thereof and the valve plates and/or in the discharge ports of the valve plates. The high pressure residual gas is subsequently expanded in the cylinder bores in the phase of a suction operation in response to the movement of the pistons toward the bottom dead center. The expansion of the residual high pressure gas in the cylinder bores blocks fresh suction of the refrigerant gas before compression from the suction chambers into the respective cylinder bores in the phase of an initial stage of the suction operation. Namely, an amount of the suction of the refrigerant gas into the respective cylinder bores is reduced. Therefore, a volumetric compression efficiency of the compressor attributed to a given amount of loss of suction pressure occurs.
To overcome the above-mentioned defect of the conventional reciprocating-piston type compressor with the flapper-type suction valve mechanism, Japanese Unexamined Patent Application (Kokai) No. 5-71467 (JP-A-5-71467) filed by Kabushiki Kaisha Toyoda Jidoshokki Seisakusho corresponding to the Assignee company of the present U.S. Patent Application has proposed a reciprocating-piston type compressor provided with a suction valve mechanism improved so as to appreciably increase the volumetric compression efficiency of the compressor.
In the proposed reciprocating-piston type compressor of JP-A-5-71467, a rotary type suction valve element connected to a drive shaft to be rotated together with the drive shaft is used for successively supplying respective cylinder bores of the compressor with suction refrigerant gas during the rotation thereof in a cylindrical chamber centrally recessed in the cylinder block of the compressor. The rotary-type suction valve element has a suction passageway formed therein to provide a fluid communication between a suction chamber of the compressor and the respective cylinder bores in the suction phase, via communication passageways radially extending between the cylindrical chamber and the respective cylinder bores of the cylinder block. The use of the rotary-type suction valve element is effective for smoothly and constantly supplying the refrigerant gas from the suction chamber into respective cylinder bores.
Further, the rotary-type suction valve element of the compressor of JP-A-5-71467 is also provided with a bypass passageway for routing residual refrigerant gas, i.e., the part of the compressed refrigerant gas remaining in respective cylinder bores without being discharged therefrom at the final stage of the discharging phase, toward respective cylinder bores which are at the initial stage of the compression phase. Accordingly, a loss of suction pressure in each of the respective cylinder bores of the compressor of JP-A-5-71467 can be appreciably reduced. Thus, the reciprocating-piston type compressor is able to exhibit an adequate volumetric compression efficiency.
Another reciprocating-piston type refrigerant compressor with an improved rotary valve has been proposed in Japanese Patent Application No, 4-33645 filed by Kabushiki Kaisha Toyoda Jidoshokki Seisakusho corresponding to the Assignee company of the present U.S. Patent Application, and will be published by the Japanese Patent Office at around the end of 1993 or the beginning of 1994. The rotary valve of the compressor is provided with a suction passageway for successively distributing a refrigerant gas before compression supplied from a suction chamber into respective cylinder bores during rotation thereof, and also a grooved passageway means formed in the outer circumference thereof for capturing the compressed refrigerant gas when it leaks from the cylinder bores in the phase of a discharging operation to thereby quickly route the captured gas toward the respective cylinder bores in the phase of an initial stage of compressing operation after the completion of the suction operation, (i.e., the cylinder bores in which the corresponding pistons are at the bottom dead center thereof to start the compressing stroke ). Accordingly, the leaking refrigerant gas can be re-compressed in the respective cylinder bores in the phase of compressing operation. Thus, the leaking gas under high pressure will not subjected to expansion. Therefore, the respective cylinder bores are able to pump in a sufficient amount of the refrigerant gas before compression during the suction-operation phase to thereby maintain an adequate volumetric compression efficiency.
However, the compressors of JP-A-5-71467 and Japanese Patent Application No. 4-33645 still suffer from the defects described below.
When one of these compressors is driven by a drive force given to the drive shaft, the rotary-type suction valve rotates in the cylindrical chamber of the cylinder block so as to distribute the refrigerant gas into respective cylinder bores in the suction phase. The rotary-type suction valve element is constantly in sliding contact with the inner wall of the cylindrical chamber, and accordingly, the inner wall of the cylindrical chamber functions as an air-tight valve seat capable of preventing the refrigerant gas under high pressure from leaking from respective cylinder bores. It is, however, impossible to completely prevent a part of the refrigerant gas under high pressure from leaking out of respective cylinder bores in the compressing and/or discharging phases into the contacting area between the cylindrical chamber and the rotary-type suction valve element by way of the afore-mentioned radial communication passageways of the cylinder block.
At this stage, since the compressors of JP-A-5-71467 and of Japanese Patent Application No. 4-33645 are not provided with any means for appropriately returning the leaking refrigerant gas toward respective cylinder bores in the compressing and/or discharging phase, the refrigerant gas leaking from the contacting area between the cylindrical chamber and the rotary-type suction valve element gradually enters a lower pressure region within the compressor body such as the suction chamber communicating with the cylindrical chamber of the cylinder block, the wobble plate chamber or crank chamber communicating with one end of the rotary-type suction valve element, and the suction passageway of the valve element per se. Consequently, the lowering of the volumetric compression efficiency of the compressor cannot be avoided. The lowering of the volumetric compression efficiency brings about a reduction in the amount of the compressed refrigerant gas circulating through the air-conditioning system, Further, in spite of the above-mentioned lowering of the volumetric compression efficiency and the reduction in the circulating amount of the compressed refrigerant gas, the drive force necessary for operating the compressor is not reduced, and thus a ratio between the drive force presented to the compressor by an external drive source such as an automobile engine and a work done by the compressor, i.e., the drive force-to-work efficiency is low, and the temperature of the compressed refrigerant gas measured at the delivery port of the compressor is high. This high temperature of the compressed refrigerant gas adversely affects the function of the condenser of the air-conditioning system, and accordingly, the performance of the air-conditioning system is degraded.